In the semiconductor industry, an ever-increasing desire exists to manufacture smaller structures with high accuracy and reliability. Lithography is a critical part of such manufacturing process. In a mask-less lithography system, charged particle beamlets may be used to transfer a pattern onto a target. The beamlets may be individually controllable to obtain the desired pattern.
To be commercially viable, the charged particle lithography systems need to be able to meet challenging demands for substantial wafer throughput and stringent error margins. A higher throughput may be obtained by using more beamlets, and hence more current.
However, the handling of a greater number of beamlets results in the need for more control circuitry. The operational control circuitry may cause heating within the lithography system. Furthermore, an increase in the current results in more charged particles that interact with components in the lithography system. The collisions between charged particles and system components inside the lithography system may cause significant heating of respective components. The resulting heating of beam manipulation components may lead to thermal deformations that reduce the accuracy of the lithography process.
The use of a large number of beamlets further increases the risk of unacceptable inaccuracy due to inter-particle interactions between the beamlets (e.g. Coulomb interactions).
The effects of inter-particle interactions may be reduced by shortening the path between particle source and target. Path shortening may be achieved by using stronger electric fields for manipulating the charged particles, which requires application of larger electric potential differences between various electrodes in the charged particle lithography system.
With stronger electric fields present, mechanical misalignments in the particle source, the field electrodes, and other beam manipulation elements (e.g. misalignment resulting from mechanical resonances) will have a larger impact on the field accuracy, and hence on the beam processing accuracy.
Also, with stronger electric fields, any temporary changes in the geometrical configuration of the beam manipulation elements increases the risk of electric discharge, which can have detrimental consequences for the system's structural integrity and achievable accuracy.